Tool String Threads

ABSTRACT

A downhole tool string component comprises a tubular body with a first and second end. The tubular body of the tool string comprises an inner surface and an outer surface. A loading member near the other end of the tubular component is disposed about the outer surface and is adapted for loading the at least one sleeve against a shoulder. The loading member comprises an internal threadform adapted to threadingly engage an external threadform in the outer surface of the tubular body. Either the external threadform or the internal threadform comprises a plurality of threads with a distal thread comprising a first thread height and a proximal thread comprising a second thread height. The first thread height is greater than the second thread height and a plurality of the threads heights between the first and second thread heights accumulatively taper from the first height to the second height.

BACKGROUND OF THE INVENTION

The current application relates to downhole drilling. During downholedrilling torque acts on downhole drilling tools which if directedtowards drilling instrumentation can lead to their failure. Thesedevices may be very expensive to replace and if damaged could lead todrilling delays and other possible failures.

U.S. Pat. No. 6,447,025 to Smith, which is herein incorporated byreference for all that it contains discloses an oilfield tubular memberthat includes a pin member and a box member, each have a tapered thread.The pin thread has a root, a crest, a pressure flank, and a stab flank.The box thread has a root, a crest, a pressure flank, and a stab flank.The pin crest has a stab flank pin crest radius and a pressure flank pincrust radius which is at least twice the radius. The improved oilfieldconnection minimizes damage to the connection during misalignment of thepin member and box member.

U.S. Pat. No. 5,492,375 to Smith, which is herein incorporated byreference for all that it contains discloses a tubular drill pipe havinga pin connector at one end and a box connector at the other end has eachconnector adapted to mate with a connector similar to that at theopposite end of the pipe—but on another pipe, to form a tool joint. Theconnectors are of the type having two pair of axially abutting make-upfaces; a primary annular shoulder formed at the inner end of the base ofthe pin connector, and an internal secondary shoulder at the innerextremity of the base of the box connector which abuts the end of anoutermost nose section of the pin connector.

U.S. Pat. No. 3,651,678 to Zook et al., which is incorporated byreference for all that it contains discloses a through feed threadrolling die for rolling external threads on a cylindrical work piece hasan external thread thereon with relieved starting and finishingsections, the starting relief providing flat crests which form apredetermined angle with the roll axis and taper to a diameter at thestarting end less than the mean height of the fully formed threads. Amodified version tapers the starting section at the larger angle thanthe predetermined angle of the crests thereby reducing the length of thestarting section. The invention includes the method of metal movementcaused by the die in the formation of the thread.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the invention, a downhole tool string componentcomprising a tubular body with a first and second end. The tubular bodyof the tool string comprises an inner surface and an outer surface. Atleast one sleeve is mounted about the outer surface of the tubular body.The tubular body comprises a shoulder near either the first or secondend and is in mechanical communication with the at least one sleeve. Aloading member near the other end of the tubular component is disposedabout the outer surface and is adapted for loading the at least onesleeve against the shoulder. The loading member comprises an internalthreadform adapted to threadingly engage an external threadform in theouter surface of the tubular body. Either the external threadform or theinternal threadform comprises a plurality of threads with a distalthread comprising a first thread height and a proximal thread comprisinga second thread height. Wherein the first thread height is greater thanthe second thread height and a plurality of the threads heights betweenthe first and second thread heights accumulatively taper from the firstheight to the second height.

The shoulder of the tubular body may be formed on the outer surface. Theshoulder may be an attachment to the outer surface. The shoulder mayalso be threadedly attached to the outer surface of the tubular body.

The thread heights may be formed in part from machining. The threadheights may be truncated. The threads of the internal threadform maycomprise substantially equal heights. The threads of the externalthreadform may also comprise substantially equal heights. The externalthreadform may be between 5 and 9 inches long. The external threadformmay also comprise tapered threads. The internal and external threadformsmay be straight threads. One threadform from the internal threadform orthe external threadform may be truncated while the other may benontruncated. A pocket may be provided between the at least one sleeveand the outer surface of the tubular body. The downhole instrumentationmay be secured within the pocket. The accumulative taper may be between0.1-5 degrees from the loading member to the shoulder. The sleeve may berotationally fixed to the tubular body. A stress relief groove may bedisposed in the outer surface adjacent and proximal to the externalthreadform.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an orthogonal diagram of an embodiment of a tool string.

FIG. 2 is a cross-sectional diagram of an embodiment of a tool stringcomponent.

FIG. 3 is another cross-sectional diagram of an embodiment of a toolstring component.

FIG. 4 is another cross-sectional diagram of an embodiment of a toolstring component.

FIG. 5 is another cross-sectional diagram of an embodiment of a toolstring component.

FIG. 6 is another cross-sectional diagram of an embodiment of a toolstring component.

FIG. 7 is another cross-sectional diagram of an embodiment of a toolstring component.

FIG. 8 is another cross-sectional diagram of an embodiment of a toolstring component.

FIG. 9 is another cross-sectional diagram of an embodiment of a toolstring component.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT

FIG. 1 is an orthogonal diagram of an embodiment of a tool string 100comprising a drill bit 102 located at the bottom of a bore hole. Thetool string 100 may be made of rigid drill pipe, drill collars, heavyweight pipe, jars, and/or subs. The tool string 100 may also comprise asleeve 203 that may be adapted to protect downhole instrumentation. Asthe drill bit 102 rotates downhole the tool string 100 advances fartherinto the formation 105 due to the weight on the drill bit 102 and acutting action of the drill bit 102.

A downhole tool string component 200 in the tool string 100 may comprisea plurality of pockets 201, as in the embodiment of FIG. 2. The pockets201 may be formed by a plurality of flanges 202 disposed around thecomponent 200 at different axial locations and covered by individualsleeves disposed between and around the flanges 202. A first pocket 206may be formed around an outer diameter 204 of a tubular body 205 by afirst sleeve 207 disposed around the tubular body 205 such that oppositeends of the first sleeve 207 fit around at least a portion of a firstflange 208 and a second flange 209. A second pocket 210 may be formedaround the outer diameter 204 of the tubular body 205 by a second sleeve211 disposed around the tubular body 205 such that opposite ends of thesecond sleeve 211 fit around at least a portion of the second flange 209and a third flange 212. A third pocket 213 may also be formed around theouter diameter 204 of the tubular body 205 by a third sleeve 214disposed around the tubular body 205 such that opposite ends of thethird sleeve 214 fit around at least a portion of the third flange 212and a fourth flange 215. The sleeves may be interlocked or keyedtogether near the flanges 202 for extra torsional support.

The individual sleeves may allow for better axial and torsionalflexibility of the component 200 than if the component 200 comprised asingle sleeve 203 spanning the pockets 201. The sleeve may also comprisea plurality of grooves adapted to allow the sleeves to stretch and/orflex with the tubular body 205. At least one sleeve may be made of a nonmagnetic material, which may be useful in embodiments using magneticsensors or other electronics. The pockets 201 may be sealed, though asleeve and the pocket may comprise openings adapted to allow fluid topass through the sleeve such that one of the pockets is a wet pocket.

Downhole instrumentation may be disposed within at least one of thepockets of the tool string component 200. An instrumentation housing 216may be disposed within at least one of the pockets wherein the downholeinstrumentation may be disposed, which may protect the equipment fromdownhole conditions. The instrumentation may comprise sensors formonitoring downhole conditions. The sensors may include pressuresensors, strain sensors, flow sensors, acoustic sensors, temperaturesensors, torque sensors, position sensors, vibration sensors, geophones,hydrophones, electrical potential sensors, nuclear sensors, or anycombination thereof. Information gathered from the sensors may be usedeither by an operator at the surface or by the closed-loop systemdownhole for modifications during the drilling process. If the downholeinstrumentation is disposed in more than one pocket, the pockets may bein electrical communication, which may be through an electricallyconductive conduit disposed within the flange separating them.

Now referring to FIG. 3, a loading member 380 may abut one of thesleeves 203 disposed around the tubular body 205 at a first end 302 ofthe tool string component 200. The loading member 380 is adapted to forma primary shoulder 301 of the component for connection to an adjacenttool string component. The loading member may also lock the sleeve 203in place. In some embodiments, the loading member is threaded in adifferent direction than either the sleeves or thread adapted forconnection to the adjacent tool string component.

The loading member 380 may be threadedly attached to the externalthreadforms 350 of a tubular body 205. The internal threads 305 of theloading member 380 may comprise a first thread height 306 that isgreater than a second thread height 307. The height differential fromthe first thread 306 and second threads 307 may comprise a 0.1-5 degreetaper. The internal threadform 305 and the external threadform 350 maycomprise a substantially similar spacing between each individual thread304. The external threadform 350 of the tubular body 205 may betruncated.

FIG. 4 is another cross-sectional diagram of an embodiment of a toolstring component 200. The external threadform 350 on the tubular body205 may comprise individual threads with the first thread 306 comprisinga greater height than the second thread 307. Threadform 305 comprises aplurality of threads with a substantially consistent height. When thethreadforms 350, 305 are engaged the engagement surface diminishes fromthe distal thread to the proximal thread. The height differential maycomprise a 0.1-5 degree taper. This may allow for more compliancybetween the attachment of the loading member 380 and the tubular body205 and may prevent breakage. The external threadforms 350 and internalthreadform 305 may extend over half the distance of the tool stringcomponent 200. Large amounts of torque may be applied to the tool stringcomponent 200 in downhole conditions. The thread geometry, as shown inFIG. 4, may aid in protecting the tool string component 200 andinstrumentation in the tool string component 200 from torsion forces.These instrumentations may be very expensive to replace and if damagedcould lead to drilling delays and other possible failures. Torsionforces may travel from the proximal end 400 of the loading member 380through the distal end 401 along the taper. The threadform may furthercomprise a relief groove 402 that may decrease the occurrence of stressrisers in the tool string. The loading member may lock into place by athe tool joint 450 of an adjacent tool string component.

FIG. 5 is another cross-sectional diagram of an embodiment of a toolstring component 200. The internal threadforms 305 and the externalthreadforms 350 may extend two-thirds the length of the tool stringcomponent 200. The threads 304 of the loading member may comprise a0.1-5 degree taper and may be truncated. The internal threadform 305 andthe external threadform 350 may be linear such as shown in FIG. 6.

Referring now to FIG. 7 the internal threadform 305 and externalthreadform 350 may be less than half the length of the tool stringcomponent 200. The external threadform 350 may also comprise a truncatedgeometry, and the internal threadform 305 may comprise a nontruncatedgeometry. The threadforms may be spaced 0.5-0.3 inches.

FIG. 8 is another cross-sectional diagram of an embodiment of a toolstring component 200. The external threadform 350 may comprise a castleor course thread that engages the internal threadform 305. The externalthreadform 350 may comprise a first thread 306 with a height larger thanthe second thread 307 which may comprise a taper. This geometry mayspread load forces that may occur during downhole drilling and preventpremature breakage and stress fractures.

FIG. 9 is another cross-sectional diagram of an embodiment of a toolstring component 200. The tool string component 200 may compriseinternal threadforms 305 and external threadforms 350. The geometry ofthe external threadform 350 may comprise a linear geometry from theproximal end 400 of the loading member 380 and a taper geometryextending to the distal end 401 of the loading member 380. The taper maybe 0.1-5 degrees from the middle of the threadform to the shoulder. Theinternal threadform may comprise a linear geometry from the proximal end400 to the distal end 401.

Whereas the present invention has been described in particular relationto the drawings attached hereto, it should be understood that other andfurther modifications apart from those shown or suggested herein, may bemade within the scope and spirit of the present invention.

1. A downhole tool string component, comprising: a tubular body with a first and second end, the tubular body comprising an inner surface and an outer surface; at least one sleeve is mounted about the outer surface of the tubular body; the tubular body comprising a shoulder near either the first or second end and being in mechanical communication with the at least one sleeve; a loading member near the other end of the tubular component is disposed about the outer surface and is adapted for loading the at least one sleeve against the shoulder; the loading member comprising an internal threadform adapted to threadingly engage an external threadform in the outer surface of the tubular body; either the external threadform or the internal threadform comprising a plurality of threads with a distal thread comprising a first thread height and a proximal thread comprising a second thread height; wherein the first thread height is greater than the second thread height and a plurality of the threads heights between the first and second thread heights accumulatively taper from the first height to the second height.
 2. The component of claim 1, wherein the shoulder is formed on the outer surface.
 3. The component of claim 1, wherein the shoulder is an attachment to the outer surface.
 4. The component of claim 3, wherein the shoulder is threadedly attached to the outer surface.
 5. The component of claim 1, wherein the thread heights are formed in part from machining.
 6. The component of claim 1, wherein the thread heights are truncated.
 7. The component of claim 1, wherein the threads of the internal threadform comprise substantially equal heights.
 8. The component of claim 1, wherein the threads of the external threadform comprise substantially equal heights.
 9. The component of claim 1, wherein a radial pocket is provided between the at least one sleeve and the outer surface of the tubular body.
 10. The component of claim 9, wherein downhole instrumentation is secured within the pocket.
 11. The component of claim 1, wherein the accumulative taper is between 0.1-5 degrees.
 12. The component of claim 1, wherein the external threadform is between 5 and 9 inches long.
 13. The component of claim 1, wherein the threadform comprises a plurality of threads 0.1 to 0.25 inches thick.
 14. The component of claim 1, wherein the external threadform comprises tapered threads.
 15. The component of claim 1, wherein the internal and external threadforms are straight threads.
 16. The component of claim 1, wherein the sleeve is rotationally fixed to the tubular body.
 17. The component of claim 1, wherein a stress relief groove is disposed in the outer surface adjacent and proximal to the external threadform.
 18. The connection of claim 1, wherein one threadform either the internal threadform or the external threadform are truncated while the opposing threadform is non truncated.
 19. The connection of claim 1, wherein a threadform comprises a linear geometry near the loading element and a taper near the shoulder.
 20. A downhole tool string component, comprising: a tubular body with a first and second end, the tubular body comprising an inner surface and an outer surface; the loading member comprising an internal threadform adapted to threadingly engage an external threadform in the outer surface of the tubular body; either the external threadform or the internal threadform comprising a plurality of threads with a distal thread comprising a first thread height and a proximal thread comprising a second thread height; wherein the first thread height is greater than the second thread height and a plurality of the threads heights between the first and second thread heights accumulatively taper from the first height to the second height. 